I bought one of these wheel clamps ....
https://amzn.to/47KeoFG
I really only used it on the trailer in the driveway as a visual deterent, but have also put it on the motorhome if going away for a time and leaving the van in the driveway - again, as a visual deterrent. I am a believer that putting people off the idea of stealing something is better than having something that tells them after they have broken in.
I also bought one of these -
https://amzn.to/3JhRGeO
I prefer these to the big locks that covers the entire wheel as much easier to store out the way. (and it generally lives under one of the side sofas and is very rarely used TBH). But I can put it on if leaving the motorhome in an area I am not too keen on. But to be frank, if I am thinking 'oh, I need to get the steering lock on in this place' I am more likely to move on to somewhere else anyway.
My next bit of 'defence' is the fitting of a small home alarm into the Motorhome. I have this one -
https://amzn.to/49jhL7K - plus various add-ons.
This particular one is not currently available but there are quite a few equivalent ones.
What is good about this kind of system is you can add on things like PIR detectors and link the system to cameras plus have it connected via the internet to services like Amazon Alexa. So I have the mag sensors on all the Doors and Windows, plus external locker doors, as well as 2 PIR sensors and a Blink Camera. It is connected to the Alexa Echo in the van so if someone opens a door with the alarm set, the Alexa will tell them they are being recorded and I get an message saying there is an intruder.
These alarm systems are not expensive and are simple to fit. You could get a very simple 'shed alarm' as well which you just set with a remote when you leave the van and protects the van same as you would protect a shed or garage. Again, very cheap but effective.